Weld terminal, switch assembly and methods of attachment

ABSTRACT

A terminal and electrical contact for a pair of leads of an electrical component is provided, the terminal having a pair of terminals each comprising a planar member comprising a conductive material that surrounds an opening in the planar member; and wherein one of the pair of leads is welded to one of the pair of terminals such that the lead traverses the opening and is welded to the terminal at a portion of the terminal adjacent to the opening and the other one of the pair of leads is welded to the other one of the pair of terminals such that the lead traverses the opening and is welded to the terminal at a portion of the other one of the pair of terminals adjacent to the opening.

BACKGROUND

Exemplary embodiments of the present invention relate to a weldterminal, switch assembly and methods of attaching leads to a terminal.

The joining of switch leads to lead frame terminals is typicallyaccomplished by soldering, laser welding or a resistance weldingprocesses. Soldering processes are the most widely used because of theterminal material type and the terminal geometry and/or configuration.The switch leads and lead frame terminals are typically made of brass,bronze or copper and due to their inherent high electrical conductivity,the resultant low resistance creates less than optimal conditions forstandard resistance welding processes. The lead frame terminal geometrycan be restrictive due to physical size constraints and subsequentmolding processes where part flashing is possible.

Accordingly, it is desirable to weld terminal and method of welding thatprovides an improved weld and method for attachment.

SUMMARY OF THE INVENTION

In one embodiment, a terminal and electrical contact for a pair of leadsof an electrical component is provided, the terminal having a pair ofterminals each comprising a planar member comprising a conductivematerial that surrounds an opening in the planar member; and wherein oneof the pair of leads is welded to one of the pair of terminals such thatthe lead traverses the opening and is welded to the terminal at aportion of the terminal adjacent to the opening and the other one of thepair of leads is welded to the other one of the pair of terminals suchthat the lead traverses the opening and is welded to the terminal at aportion of the other one of the pair of terminals adjacent to theopening.

In another embodiment a switch assembly is provided, the switch assemblyhaving a switch having a pair of conductive leads extending therefrom; apair of terminals extending from a switch housing, each terminalcomprising: a conductive material that surrounds an opening; and whereinone of the pair of leads is welded to one of the pair of terminals suchthat the lead traverses the opening and is welded to the terminal at aportion of the terminal adjacent to the opening and the other one of thepair of leads is welded to the other one of the pair of terminals suchthat the lead traverses the opening and is welded to the terminal at aportion of the other one of the pair of terminals adjacent to theopening.

In another embodiment a method for joining a lead of a switch to aterminal is provided, the method comprising: resistance welding a pairof conductive leads of the switch to a pair of terminals extending froma switch housing, each terminal comprising a conductive material thatsurrounds an opening; and wherein one of the pair of leads is welded toone of the pair of terminals such that the lead traverses the openingand is welded to the terminal at a portion of the terminal adjacent tothe opening and the other one of the pair of leads is welded to theother one of the pair of terminals such that the lead traverses theopening and is welded to the terminal at a portion of the other one ofthe pair of terminals adjacent to the opening.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features, advantages and details appear, by way of example only,in the following description of embodiments, the description referringto the drawings in which:

FIG. 1 is a perspective view of a switch assembly in accordance with anexemplary embodiment of the present invention;

FIG. 2 is a plan view illustrating a switch lead welded to a frame leadin accordance with an exemplary embodiment of the present invention;

FIG. 3 is view along lines 3-3 of FIG. 2;

FIGS. 4-6 are views of welds made using exemplary embodiments of thepresent invention; and

FIG. 7 is a plan view of a switch lead welded to a frame lead inaccordance with an alternative exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION

In accordance with various embodiments of the present invention a weldterminal, switch assembly and method of securing a switch lead to a weldor frame terminal is provided. In one embodiment and referring now toFIG. 1 a switch assembly 10 in accordance with an exemplary embodimentof the present invention is illustrated. The switch assembly has aswitch 12 such as a micro switch or an electrical component with a pairof leads 14, 16 extending from a housing 18 of the switch. Leads 14 and16 comprise an electrically conductive material. In one non-limitingembodiment, the switch will have a depressible or movable actuator 20whose movement thereofwill close a circuit or switch 22 (illustrated bythe dashed lines) and located within the housing. Electrically coupledto the circuit is the pair of leads 14 and 16 such that upon movement ofthe actuator a circuit between the leads is either closed or opened.

As illustrated, a pair of weld terminals 24 are shown extending from asurface 26 of a housing 28. Although a pair of weld terminals and a pairof leads are illustrated exemplary embodiments of the present inventioncontemplate numerous weld terminals as well as numerous leads thus,exemplary embodiments of the present invention are not limited to just apair of terminals and a pair of leads.

In an exemplary embodiment each terminal is formed from a planar membercomprising an electrically conductive material. In one embodiment,housing 28 has features 30 configured to engage and receive a portion ofthe housing of the switch. For example, features 30 may comprise anopening into which the housing of the switch is received. Each planarmember 24 has a central opening 32. In one embodiment, the centralopening is completely surrounded by the conductive material of theplanar member.

For example and referring now to FIGS. 2 and 3, a portion of one of theterminals is illustrated. As shown, opening 32 is surrounded by an outerperipheral portion 34 that has a dimension 36 that a portion 38 of thelead is secured to by a resistance welding process. Resistance weldingis a process used to join metallic parts with electric current.Referring now to FIG. 3 a side view of the terminal/lead weld securementis illustrated. As shown, the terminal is a planar member having athickness 40, which is substantially planar providing a flat surface toweld the lead to with a welding process namely a resistance weldingprocess.

Resistance welding is a processes wherein at least two work pieces aresecured to each other by the heat obtained from resistance of the workpieces to an electric current in a circuit of which the work piece is apart and by the application of pressure to the two work pieces. As shownin FIG. 3 a pair of electrodes 42, 44 apply a force to the work pieces(lead 14 and terminal 24) in the directions of arrows 46 and 48 while acurrent is applied through electrode 42, portion 38 of lead 14, portion34 of terminal 24 and electrode 44 wherein the heat generated will causeeither or both of portion 38 and 34 to melt and form a weld 50.

The size and shape of the individually formed welds are limitedprimarily by the size and contour of the electrodes. Thus, the use of aplanar terminal and substantially planar lead allows a generally flatsurface to be placed between the two electrodes. Furthermore and throughthe use of opening 32 dimension 36 causes the heat to be generatedbetween the lead portion and the terminal portion. The reduced area forresistance welding reduces the weld contact area and does not requireany bumps or special modification that would hinder injection moldingprocesses.

The welding cycle must first develop sufficient heat to raise a smallvolume of metal to the molten state. This metal then cools while underpressure until it has adequate strength to hold the parts together. Thecurrent density and pressure must be sufficient to produce a weldnugget, but not so high as to expel molten metal from the weld zone.

In all forms of resistance welding, the parts are locally heated until amolten pool forms. The parts are then allowed to cool, and the poolfreezes to form a weld nugget. To create heat, electrodes pass anelectric current through the work pieces. The heat generated depends onthe electrical resistance and thermal conductivity of the metal, and thetime that the current is applied.

The electrodes are held under a controlled force during welding. Theamount of force affects the resistance across the interfaces between thework pieces and the electrodes. The force is adjusted to immediatelycreate heat at the interface between the work pieces.

The heat needed to produce a molten pool depends on the thermalconductivity and melting point of the metal being welded. A materialwith a high thermal conductivity will quickly conduct heat away from theweld pool, increasing the total heat needed to melt the pool. A lowmelting point will lower the heat needed. Accordingly, the smallerdimension 36 of portion 34 of the terminal will reduce the surface areaof the terminal directly beneath the portion 38 of the lead beingsecured to the terminal thus reducing the amount of heat needed to weldthe two work pieces together.

FIGS. 4-6 are various views illustrating a weld 50 of a lead to aterminal in accordance with exemplary embodiments of the presentinvention.

Referring back now to FIGS. 1-3 and 5 the leads are welded to the pairof terminals such that the lead traverses the opening and is welded tothe weld terminal at one side of the opening. In an alternativeembodiment, the lead may also be secured to the terminal at an oppositeside of the opening where the lead traverses another portion 60 of theterminal shown in the area 62 of the dashed lines in FIG. 2. Accordinglyand in this embodiment, the lead is secured to the terminal at twolocations using a resistance welding process.

Accordingly and referring to FIG. 1 each of the leads are secured to theterminals at at least one location adjacent to opening 32 oralternatively at two locations opposite opening 32.

In still another alternative embodiment and referring now to FIG. 7 aplanar terminal 124 is shown with an opening 132 that is not completelysurrounded by portions of terminal 124 and a portion 138 of lead 114 isresistance welded to a portion 134 of terminal 124.

The flat geometry of the lead frame terminals 24 are suitable forover-molding processes wherein the housing 28 is molded about theterminals, while the “hole” and “notch” shapes of the terminals providegood switch lead retention during the welding process.

Weld projection theory proposes increasing electrical resistance bydecreasing contact surface area between the components to be joined. Bytaking advantage of the small side of the switch lead and mating up to athin terminal frame section, a high resistance zone is created. Theaperture geometry wherein the lead is supported on both sides providesstructural support to the weld. In addition to welding advantages, theflat geometry of this design can be properly shut-off in the moldingprocess and prevent un-wanted material from flashing into the aperturearea.

In one embodiment, the thickness of the lead area contacting theterminal is 0.4 mm of course, other dimensions greater or less than 0.4mm are contemplated in accordance with exemplary embodiments of thepresent invention.

In one embodiment, a method for welding leads to a planar terminal isprovided. First a plurality of planar terminals are formed by a stampingor other suitable process wherein an opening is provided in the terminaland then a terminal or terminals are insert molded into an housing thena switch with terminals are placed into the housing such that a portionof a lead of the switch traverses the opening then a current and forceis applied by a pair of electrodes wherein a weld is provided betweenthe lead and the terminal. In an alternative embodiment, the lead iswelded to the terminal prior to the insert molding process. In stillanother embodiment, the lead is welded at two locations on oppositesides of the opening of the terminal.

While the present invention has been described in terms of specificembodiments, it should be appreciated that the spirit and scope of theinvention is not limited to those embodiments. The features, functions,elements and/or properties, and/or combination and combinations offeatures, functions, elements and/or properties of the track set may beclaimed in this or a related application. All subject matter which comeswithin the meaning and range of equivalency of the claims is to beembraced within the scope of such claims.

1. A terminal and electrical contact for a pair of leads of anelectrical component, the terminal comprising: a pair of terminals eachcomprising a planar member comprising a conductive material thatsurrounds an opening in the planar member; and wherein one of the pairof leads is welded to one of the pair of terminals such that the leadtraverses the opening and is welded to the terminal at a portion of theterminal adjacent to the opening and the other one of the pair of leadsis welded to the other one of the pair of terminals such that the leadtraverses the opening and is welded to the terminal at a portion of theother one of the pair of terminals adjacent to the opening.
 2. Theterminal and electrical contact as in claim 1, wherein the opening iscompletely surrounded by the conductive material of the terminal.
 3. Theterminal and electrical contact as in claim 2, wherein the opening isrectangular in shape and the terminal is rectangular in shape.
 4. Theterminal and electrical contact as in claim 1, wherein the pair ofterminals are insert molded into a plastic housing.
 5. The terminal andelectrical contact as in claim 4, wherein the opening is completelysurrounded by the conductive material of the terminal.
 6. The terminaland electrical contact as in claim 5, wherein the opening is rectangularin shape and the terminal is rectangular in shape and each of the pairof leads are welded on opposite side of the opening.
 7. The terminal andelectrical contact as in claim 1, wherein the pair of terminals have asubstantially flat profile.
 8. A switch assembly, comprising: a switchhaving a pair of conductive leads extending therefrom; a pair ofterminals extending from a switch housing, each terminal comprising: aconductive material that surrounds an opening; and wherein one of thepair of leads is welded to one of the pair of terminals such that thelead traverses the opening and is welded to the terminal at a portion ofthe terminal adjacent to the opening and the other one of the pair ofleads is welded to the other one of the pair of terminals such that thelead traverses the opening and is welded to the terminal at a portion ofthe other one of the pair of terminals adjacent to the opening.
 9. Theswitch assembly as in claim 8, wherein the opening is completelysurrounded by the conductive material of the terminal.
 10. The switchassembly as in claim 9, wherein the opening is rectangular in shape andthe terminal is rectangular in shape.
 11. The switch assembly as inclaim 8, wherein the pair of terminals are insert molded into a plastichousing.
 12. The switch assembly as in claim 11, wherein the opening iscompletely surrounded by the conductive material of the terminal. 13.The switch assembly as in claim 12, wherein the opening is rectangularin shape and the terminal is rectangular in shape and each of the pairof leads are welded on opposite side of the opening.
 14. The switchassembly as in claim 8, wherein the switch is a micro-switch.
 15. Theswitch assembly as in claim 8, wherein the opening is completelysurrounded by the conductive material of the terminal and the pair ofterminals have a substantially flat profile and the switch is amicro-switch.
 16. A method of joining a switch to a terminal,comprising: resistance welding a pair of conductive leads of the switchto a pair of terminals extending from a switch housing, each terminalcomprising a conductive material that surrounds an opening; and whereinone of the pair of leads is welded to one of the pair of terminals suchthat the lead traverses the opening and is welded to the terminal at aportion of the terminal adjacent to the opening and the other one of thepair of leads is welded to the other one of the pair of terminals suchthat the lead traverses the opening and is welded to the terminal at aportion of the other one of the pair of terminals adjacent to theopening.
 17. The method as in claim 16, wherein the opening iscompletely surrounded by the conductive material of the terminal. 18.The method as in claim 16, wherein the opening is rectangular in shapeand the terminal is rectangular in shape and the pair of terminals havea substantially flat profile.
 19. The method as in claim 16, wherein thepair of terminals are insert molded into a plastic housing prior to thewelding step.
 20. The method as in claim 19, wherein the opening isrectangular in shape and the terminal is rectangular in shape and thepair of terminals have a substantially flat profile and the switch is amicro-switch and each of the pair of leads are welded on opposite sideof the opening.